Telephone plant



Nov. 29, 1932. D. c. cRowE:

TELEPHONE PLANT Filed July 6, 1931 /NvN To@ D. C. @m w@- Patented Nov.29, 1932 UNITED STATES PATENT OFFICE DOUGLAS CORMACK CROWE, OFSTOCKHOLM, SWEDEN, ASSIGNOR TO TELEFONAXTIE- IBOLAGET L. M. ERICSSON, FSTOCKHOLM, SWEDEN, A COMPANY 0F SWEDEN TELEPHONE PLANT Application.v led.Tuly 6, 193,1; Serial No. 549,032, and in Sweden July 26,1930.

The present invention refers to arrange ments for selective actuation ofswitching apparatus connected to a common line and is particularlyapplicable to telephone plants in which it is desired selectively toactuate cer- Y cuits.

tain apparatus in a group of switching apparatus over a single line bymeans of current impulses of different magnitudes and directions. Theinvention may also advantageously be applied to systems with so calledparty lines, the different subscribers sets being then provided withswitching elements in accordance with the invention. In known systems ofthis kind it has been very difficult to .increase the number ofsubscribers to the desired degree while maintaining simplicity ofcircuit arrangements and construction in the telephone exchanger as wellas at the subscribers positions. The desirability of central batteryoperation has then led to ditferent circuit arrangements with condensersat the subscribers positions. Said known circuit arrangements, however,require ringing current generators for a plurality of frequencies anddoV not meet modern requirements with regard to the number of apparatusthat can be connected to a certain line.

The present invention has for its objectto eliminate inconveniences ofthe above `'kind and consists substantially therein that each switchingapparatus is provided with apolarized relay which is adapted to reactonly for current impulses of a certain kind and ywhich over twoseries-connected condensers is connected to earth, said polarized relaybeing arranged to shunt the one condenser over its resting contact andto cause the other condenser to be connected in parallel with theresistance over its operating contact. In this manner a circuitarrangement is obtained in which the condensers are charged Aovercertain circuits and discharged over other cir- The invention will bemore closely "described with reference to the accompanying drawing whichshows asan example a telephone plant having eightv subscribers setsconnected to a party line.

The upper part of the drawing shows'the party line with its branches aand b and with the subscribers sets l'to 8 connected thereto, only thoseparts being indicated which are necessary forillustrating the invention.The lower part of the drawing is intended to show those parts in thetelephone exchange which are of interest for the explanation of theinvention. For the sake of simplicity the signal device has been shownas a key set K but it is of course also conceivable to build the same ofa number of relays which, for instance, may be actuated by means ofligure impulse series from other subscribers of the exchange orv fromthe party subscribers them` selves. The signal battery B is earthed atits middlepoint and has in addition thereto four terminals, namely V,+30 V, -30 V, -60 V. With these voltages eight different combinationsmay be obtained as will be seen from the following table. v

vous volts known manner to the party line, a calling circuit being thenclosed through elements of the apparatus 8 not shown on the drawing andthrough the line relay L, the latter relay then closing, over itsoperating contact land the Contact 2 of the relay B, a circuit 3 for thecalling lamp AL which is thereby lit. The operator then connects herselfto the party line by means of the jack J, the relay Bv being thenenergized over the circuit 4 and cutting oli the line relay and theplus-potential at its contacts 5 and 6 respectively. The

operator is now able to communicate with the calling subscriber withoutbeing disturbed by any of the other party subscribers. After having beeninformed that connection with the subscriber 1 is desired the operatorfirst pushes down the key 1 of the key set and thereafter the signal keySK whereby the signal is sent out on the party line. The signal consistspartly therein that the b-wire is connected to the +3() V terminal ofthe battery over the circuit 6 and partly therein that the L-wire isconnected to the i 60 V terminal of the signal battery over the circuit7, a current impulse being thereby obtained tln'ough the polarized relayP, the condenser X, the resistance R and the resting contact 8 of therelay to earth. As at this instant the condenser Y is shunted thecondenser X is charged and the relay P attracts its armature. Thecondenser X is then parallel-connected with an auxiliary relay H overthe operating Contact 9 of the relay P, whereas the condenser Y ischarged by means of new power from the a-wire. At the same time thecondenser X is discharged over the relay H which attracts its armatureand over its operating contact 10 connects the condenser Z to the b-wirein order to be charged. As soon as the condenser Y has been charged therelay P cannot any longer hold its armature attracted wherefore thelatter returns to its normal position, the condenser X being thencharged anew. Simultaneously with the relay P also the relay H iscle-energized and the condenser Z is discharged over the polarized alarmbell PR to earth. Said alarm bell is thereby brought to carry over itsarmature once whereafter the armature is restored by means of a springcontrolling the same. The relay P is actuated again and the operation isrepeated. The discharging circuit for the condenser X thus receives asmany current impulses as the relay P wherefore the relay H vibrates intime with the relay P and consequently the same frequency of the toll ofthe alarm bell is obtained.

As will be seen from the drawing also the relays P and H of thesubscriber 2 will vibrate and the appertaining condenser Z will becharged and discharged over th-e corresponding alarm bell PR. Thealarm-bell of the subscriber 2 is, however, biased in the oppositedirection to the alarm bell in the apparatus 1, and only the latter bellwill therefore ring. It is, of course, also co-nceivablc to usepositively controlled relays in place of alarm bells, the arrangementsbeing then preferably such that the whole switching operation is carriedout only once whereafter the armatures of the relays are locked in asuitable manner. The switching arrangement may then be used forestablishing certain selecting operations. After the desired subscriberhas been called up a talking connection is established in known manner.It

is only necessary that the operator lifts the key SK whereafter thetalking circuits of the subscribers are fed from the exchange in knownmanner.

I claim 1. In a selective system a line, a number of marginal adjustedpolarized relays each being connected between any of the branches ofsaid line and earth over two series-connected condensers, means toactuate the polarized relays selectively by current impulses ofdifferent magnitudes and directions, means to shunt one of the said twocondensers when the polarized relay is at rest, and means to connect theother condenser in parallel with a resistance when the said relay isenergized.

2. A selective system as claimed in claim 1 the means to actuate thepolarized relays selectively consisting of a signal battery having smallcapacity, earthed at its middle point and provided with a plurality ofpositive and negative voltage terminals.

3. ln a selective system a line, a number' of marginal adjustedpolarized relays each being connected between any of the branches ofsaid line and earth over two series-connected eondensers, means toactuate the polarized relays selectively by current impulses ofdiil'erent magnitudes and directions, means to shunt one of the said twocondenser-s when the polarized relay is at rest, and means to connectthe other condenser in parallel with an auxiliary relay when thepolarized relay is energized.

l. In a selective system a line, a number l of marginal adjustedpolarized relays each being connected between any of the branches ofsaid line and earth over two series-connected condensers` means toactuate the polarized relays selectively by current impulses ofdifferent magnitudes and directions, means to shunt one of the said twocondensers when the polarized relay is at rest, and means to connect theother condenser in parallel with an auxiliary relay when the polarizedrelay is energized` the said auxiliary relay being provided with acontact over which the one coating of a third condenser is connected toa current source of a certain potential, the other coating of thecondenser being connected to earth.

5. In a selective system a line, a number of marginal adjusted polarizedrelays each being` connected between any of the branches of said lineand earth over two series-connected condensers, means to actuate thepolarized relays selectively by current impulses of different magnitudesand directions, means to shunt one of the said two condensers when thepolarized relay is at rest, means to connect certain potential by theauxiliary relay and then to a polarized relay.

6. In a selective system a line, a number of marginal adjusted polarizedrelays each being connected between any of the branches of said line andearth over two series-connected condensers, means to actuate thepolarized relays selec-tively by current impulses of differentmagnitudes and directions, means to shunt one of the said two condenserswhen the polarized relay is at rest, means to connect the othercondenser in parallel with an auxiliary relay when the polarized relayis energized, a third condenser the one coating of which is connected toearth while the other may be first connected to a current sourceof'certain potential by the auxiliary relay and then to a polarizedalarm bell.

7. In a selective system a line, a number of marginal adjusted polarizedrelays each being connected between any of the branches of said line andearth over two series-connected condensers, means to actuate thepolarized relays selectively by current impulses of different magnitudesand directions, means to shunt one of the said two condensers when thepolarized relay is at rest, means to connect the other condenser inparallel with an auxiliary relay when the polarized relay is energized,a third condenser the one coating of which is connected to earth whilethe other may be first connected to a current source of certainpotential by the auxiliary relay and then to a polarized alarm bellwhich is positively controlled or biased by means of a spring.

In testimony whereof I aliix my signature.

.DOUGLAS CORMACK CROWE.

